The books are the ones who are setting it and I've noticed the difference from one book to another. Sometimes, the other book is late in adjusting it and that's why whoever gets the better odds, sportsbettors know where to bet for it.
And the books have their own indicators and researchers and that's why the odds really matter and it affects the reality and possible outcome of the game.
Just like us, we analyze and so as they but they're not always correct with the analysis that they come out as to how much odds they show.